Sticker? Several years ago, there was mention of taking a hi-res photo (in this case, a 1920s speedometer), then Photoshopping it to get the colors and such correct, then saving that file and getting the final size correct, then printing a "water slide decal" of the file for placement on the instrument face. Apparently this photo-based operation is what many gauge restorers use?
With that hi-res photo file, you might check with some of the places that do vehicle wraps, to see if they can print your file and fit it to the car? Or they can do the whole deal themselves? Perhaps they have some media sizes more inline with what you need rather than a 4x8' sheet?
It would have been hard for them to have a reliable stencil to do painting on in that compound-curved area, I suspect.
CBODY67